[rmd2]

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[blueash]

Originally Posted by golfing eagles

I saw that, and the researchers believed that 278 of the false positives were related to faulty tests. But then, we have to subtract 278 from both the numerator and denominator (462-278=184/1322-278=1056) which yields a 17.4% false positive rate----you still can't use 900,000 as the denominator. So, throwing out the tests the researchers thought were defective, there's still a 1 in 6 chance that your positive home test is really negative.

I am certain that you actually know that in a low incidence event that that positive predictive value is problematic. For the readers... If we were in a smallpox epidemic and our smallpox test had a 0.01% false positive error rate it is a great test. We test everyone with smallpox looking rash, most of whom really do have smallpox, but some don't, they have bug bites, hives, or atypical chicken pox or monkey pox or cow pox. We know from sophisticated more accurate but time consuming testing that when all rashy people are tested in the middle of our smallpox epidemic that 60% really do have smallpox.

So we test 1 million rashy people. The "real" number of smallpox cases in the example would be 600,000 and we'd like to see our rapid test report the correct 600,000 people as positive. But having a false positive error rate of .01% we instead get 600,100 positive tests. It's a big nothing burger in the middle of an epidemic. Only 100 of the 600,100 positives are wrong, 0.016%. In this situation the chance that your positive test being true is over 99.9%. Great test

But instead in today's world where thanks to immunizations and vigorous public health measures and isolation and quarantine, smallpox is gone, the last case in the world being in the 1970s, if we test 1 million rashy Americans with our smallpox rapid test, we report there are 100 positive tests. In this case the chance of your test being wrong is 100%. Same test, same 1 million rashy Americans, same number of false positives.

The false positive rate on our test did not change, but because the rate of the disease changed the odds that any individual test was wrong changes. Now with smallpox gone, every single positive test is wrong. That is not because the test suddenly became more error prone, rather the prevalence of the disease changed.

In our Covid situation, the statement to which I initially responded was that the availability of at home tests would make the number of reported cases jump 1000%. I pointed out that this was wrong because positive at home tests are not going to be reported. And in reply to the claim that the at home test is useless as it is prone to false positives.. I mentioned the Canadian study

What the Canadian study showed was that in a symptom free population of adults of working age you get essentially zero [500 out of a million] false positive tests. So that proves that the tests are NOT going to jump the numbers up because healthy people are NOT going to test positive. That's all it says. We have no idea in the Canadian study how many false negatives there might have been.

GE expressed surprise at how few tests are positive given that Covid was in the community during the study period. Again, the Canadian government, even in the very Conservative western provinces, has been strongly supportive of telling ill people to not go to work, and those exposed but not ill to quarantine and not go to work. That may in part explain the low rate of positive tests. False negatives also are clearly involved.

[oldtimes]

Originally Posted by blueash

I am certain that you actually know that in a low incidence event that that positive predictive value is problematic. For the readers... If we were in a smallpox epidemic and our smallpox test had a 0.01% false positive error rate it is a great test. We test everyone with smallpox looking rash, most of whom really do have smallpox, but some don't, they have bug bites, hives, or atypical chicken pox or monkey pox or cow pox. We know from sophisticated more accurate but time consuming testing that when all rashy people are tested in the middle of our smallpox epidemic that 60% really do have smallpox.

So we test 1 million rashy people. The "real" number of smallpox cases in the example would be 600,000 and we'd like to see our rapid test report the correct 600,000 people as positive. But having a false positive error rate of .01% we instead get 600,100 positive tests. It's a big nothing burger in the middle of an epidemic. Only 100 of the 600,100 positives are wrong, 0.016%. In this situation the chance that your positive test being true is over 99.9%. Great test

But instead in today's world where thanks to immunizations and vigorous public health measures and isolation and quarantine, smallpox is gone, the last case in the world being in the 1970s, if we test 1 million rashy Americans with our smallpox rapid test, we report there are 100 positive tests. In this case the chance of your test being wrong is 100%. Same test, same 1 million rashy Americans, same number of false positives.

The false positive rate on our test did not change, but because the rate of the disease changed the odds that any individual test was wrong changes. Now with smallpox gone, every single positive test is wrong. That is not because the test suddenly became more error prone, rather the prevalence of the disease changed.

In our Covid situation, the statement to which I initially responded was that the availability of at home tests would make the number of reported cases jump 1000%. I pointed out that this was wrong because positive at home tests are not going to be reported. And in reply to the claim that the at home test is useless as it is prone to false positives.. I mentioned the Canadian study

What the Canadian study showed was that in a symptom free population of adults of working age you get essentially zero [500 out of a million] false positive tests. So that proves that the tests are NOT going to jump the numbers up because healthy people are NOT going to test positive. That's all it says. We have no idea in the Canadian study how many false negatives there might have been.

GE expressed surprise at how few tests are positive given that Covid was in the community during the study period. Again, the Canadian government, even in the very Conservative western provinces, has been strongly supportive of telling ill people to not go to work, and those exposed but not ill to quarantine and not go to work. That may in part explain the low rate of positive tests. False negatives also are clearly involved.

The negative results are the problem. They are going to give people a false sense of security given that they are only valid for a short period of time. They can test negative on one day and on the very next day they can be positive.

[PugMom]

Originally Posted by golfing eagles

Agree. These home tests have a notoriously high rate of both false positives and false negatives, thus making their predictive value fairly low. Add to that most people will probably not insert the swab far enough, thus collecting an inadequate sample leading to a false negative result. All in all, I'm afraid this home testing plan is less COVID mitigation and more COVID mitigation theater.

[jimjamuser]

Originally Posted by mtdjed

Perhaps I have missed it but are these tests going to be accepted for foreign travel COVID test requirements. If they are as accurate as stated in these posts, wouldn't they be better than getting tested at sites such as CVS and others that report results three days later.

Just think of all the people we could hire at MCO to monitor that each person properly pokes their nose and properly handles their kit disposal. Oh, I forgot, nobody needs to monitor proper use because nobody monitors CVS drive through self-testing, but TSA blindly accepts those test results to safely fly.

Don't forget to wash your hands with soap and hot water for 20 seconds before testing, just like you do in the drive through tests.

Reading the posts closely, it can be seen that a POSITIVE indication is ACCURATE. But, a negative indication means VERY little. If someone gets a POSITIVE TEST, then they have REAL knowledge. They should NOT go to work especially indoors. They should quarantine for (I think, about 8 or 10 days) to avoid giving it to someone over age 70 or a young person with various conditions. They should monitor their condition ((what condition their condition is in) and IF super sick - they should go to a Hospital.

[jimjamuser]

Reading the posts closely, it can be seen that a POSITIVE indication is ACCURATE. But, a negative indication means VERY little. If someone gets a POSITIVE TEST, then they have REAL knowledge. They should NOT go to work especially indoors. They should quarantine for (I think, about 8 or 10 days) to avoid giving it to someone over age 70 or a young person with various conditions. They should monitor their condition ((what condition their condition is in) and IF super sick - they should go to a Hospital.

[drducat]

Originally Posted by Robbie0723

CDC Guidance for when to self test.

Self-Testing | CDC

When to Consider Self-Testing

Self-tests may be used if you have COVID-19 symptoms or have been exposed or potentially exposed to an individual with COVID-19.

Even if you don’t have symptoms and have not been exposed to an individual with COVID-19, using a self-test before gathering indoors with others can give you information about the risk of spreading the virus that causes COVID-19. This is especially important before gathering with unvaccinated children, older individuals, those who are immunocompromised, or individuals at risk of severe disease.

A positive test result indicates that you likely have a current infection, and you should isolate and inform close contacts.

A negative test result indicates that you may not be infected and may be at low risk of spreading disease to others, though it does not rule out an infection. Repeating the test will increase the confidence that you are not infected. Performing serial tests, meaning two or more tests over several days with at least 24 hours between tests—with one test as close as possible to the event you will attend—improves the reliability of testing and reduces your risk of transmitting disease to others even further. Some self-tests require this type of repeat testing in the manufacturer’s instructions.

Correct sample collection is key to accurate results.

Self-Testing | CDC

Originally Posted by mtdjed

Perhaps I have missed it but are these tests going to be accepted for foreign travel COVID test requirements. If they are as accurate as stated in these posts, wouldn't they be better than getting tested at sites such as CVS and others that report results three days later.

Just think of all the people we could hire at MCO to monitor that each person properly pokes their nose and properly handles their kit disposal. Oh, I forgot, nobody needs to monitor proper use because nobody monitors CVS drive through self-testing, but TSA blindly accepts those test results to safely fly.

Don't forget to wash your hands with soap and hot water for 20 seconds before testing, just like you do in the drive through tests.

No one will provide treatment based on a home test....a positive result will require a PCR test also....go figure right~~~~~